Conventionally, a drill bit has been used as a hole drilling tool in the case of drilling a hole into concrete, stone, or the like.
There are cases where such a drill bit is used for drilling a so-called “anchor bolt hole” into a concrete surface.
Swarf and the like in the “anchor bolt hole” need to be removed as much as possible so that a certain level of strong resistance to drawing force can be obtained for a metal anchor bolt to be implanted into the hole.
Accordingly, after drilling the “anchor bolt hole”, so-called “dirt (chips) removal work” to remove swarf and the like from the inside of the hole needs to be performed. That is, in order to allow the anchor bolt to exert its predetermined function, the swarf and the like remaining in the anchor bolt hole are required to be removed before the anchor bolt is implanted into the hole.
Therefore, in conventional cases, after an anchor bolt hole is drilled by a drill bit, a dust collector's cleaning nozzle having its proximal end connected to a suction port of the collector is inserted into the anchor bolt hole, and swarf and other dirt are sucked and removed from the inside of the hole. One of such type of dust collectors is, for example, a dust collector provided by the applicant of the present application (Patent Literature 1).
There is a case where, at the time of hole drilling work, a drill bit is used which has a dust suction hole (dust suction passage) formed at the center of the drill bit tip for the purpose of collecting chips and the like produced at the drill bit tip at the same time as performing the hole drilling work. The structure of the drill bit provided with the dust suction hole is such that two cutting edge portions are formed at the drill bit tip, that is, the cutting edge portions are arranged to be spaced apart from each other with an angle of 180 degrees between them. Specifically, a dust suction hole having a greater diameter than the width of the cutting edge portions is formed in the shaft center of the bit shaft of the drill bit, and an opening at the distal end of the dust suction hole is partially and distally exposed at a position between the cutting edge portions (Patent Literature 2)